Erosion control of hydraulically-placed silty or clay-containing sands forming the bank of a body of water is a continuing problem and has met with little success on a long term basis. For example, most of the water barriers employed in the Mississippi River delta have to be continually repaired and strengthened. It is common to form dikes or water barriers of rock riprap either alone or mixed with shells, such as oyster shells. Due to the character of the land on which the dike is formed, there is generally uneven settling of the riprap material into the unstable bottom.
If a solid cement dike is employed, uneven settling of the land underneath the dike due to the weight of the dike causes cracks in the dike which are further eroded by wave action perpendicular to the dike or the current of a river moving along the face of the dike. Dikes made of rock riprap and shell or other materials are also subjected to the erosion caused by the flowing river or waves caused by passing ships or barges. Most types of dikes presently used in river delta environment are constantly in need of repair.